Phorbol ester tumor promoters and epidermal growth (EGF) elicit a similar range of responses in cultured cells. The interaction of the tumor promoter TPA with cell surface-disposed EGF receptors suggests the possibility that phorbol esters and EGF induce their biological effects through a similar mechanism. EGF has been shown in cultured mouse cells to greatly increase the appearance of cDNA molecules homologous to VL30 genes, a family of moderately repetitive DNA sequences with many of the structural characteristics of retroviruses and transposon elements. The VL30 genes also contain long terminal repeats (LTR's) which have been shown to have characteristics of gene enhancers and insertion elements, and have been shown to be responsible for oncogenesis in some systems by insertion near cellular oncogene sequences. A major goal of this proposal is to examine the role of both the phorbol esters and EGF in the induction of transcriptional activity of VL30 (and other EGF-inducible genes) and to determine whether induction of VL30-specific RNA sequences results in the insertion of VL30 DNA elements into novel chromosomal sites. Detection of VL30 gene insertion will be made by Southern blotting of restriction endonuclease-digested DNA and hybridization to nick-translated VL30 cDNA. Appearance of VL30 in novel chromosomal sites will be tested in cultured cell lines and mouse primary epidermal cell cultures after continuous exposure to EGF and/or TPA. Transposition of VL30 elements will also be tested in papillomas and carcinomas of mouse skin following initiation by DMBA and promotion by TPA. Potential problems in detection, which may result from VL30 redundancy in the genome, will be overcome by transplantation of single VL30 genes (e.g., mouse) to heterologous cells (e.g., rat). Analysis of specific poly (A)+ molecules induced by EGF and TPA should indicate the similarities and dissimilarities of each compound in eliciting a biological response. The time of appearance of specific poly(A)+ molecules should indicate whether the two compounds may act at similar cellular sites. Our continuing structural analysis of intracellular processed EGF molecules and the effects of their microinjection on induction of specific genes should elucidate the role of EGF processing in the biological activity of EGF.